What you "install" of Ionic is the Ionic CLI, current stable version 2.2.2 at the time of writing.
When you already have a project, just check it out from Git (or your respective version management tool) and it will contain a
package.json that contains the version info for the Ionic Framework version used (called
ionic-angular in there).
Ionic Native is another library for using Native Cordova plugins in Ionic and also recently upgraded from 2.x to 3.x with some breaking changes.